1. Field of the Invention
The present invention relates to an infrared imaging device, a fixed pattern noise calculation method, and a computer readable medium storing a fixed pattern noise calculation program.
2. Description of the Related Art
In the related art, in an infrared imaging device, intrinsic fixed pattern noise (hereinafter, it is abbreviated as FPN) of devices such as a variation in sensitivity of an infrared detection pixel and a variation in gain and offset of a circuit is generated. In particular, in an infrared imaging device having imaging elements in which infrared detection pixels are two-dimensionally arranged, characteristics of each infrared detection pixel fluctuate, and thus FPN which is changed for a relatively long time is generated.
When such FPN is generated in the infrared imaging device, even in case where images of surfaces having a uniform temperature are captured, a captured image having uniform brightness (density) cannot be obtained. For the reason, in the infrared imaging device, shutter is provide in the device, FPN is calculated in a state where light incident to an infrared detection pixel from the outside is blocked, and FPN is corrected (for example, see JP2009-089138A and JP1998-115557A (JP-H10-115557A)).
However, in a method of calculating FPN in a state where a shutter is closed, the shutter is periodically closed during an operation of the infrared imaging device. Therefore, while a motion picture is being captured, the motion picture captured is periodically interrupted.
For the reason, a method of calculating FPN without using a shutter is proposed (for example, see JP2001-509996A and JP2001-336983A).
JP2001-509996A discloses technique of calculating FPN using a captured image obtained in a focused state and a captured image obtained in a non-focused state.
JP2001-336983A discloses technique of calculating FPN using a captured image obtained when an optical system is in a defocused state.